1. Field of the Invention
This invention relates to a method and apparatus for recording moving picture data encoded using a prediction encoding system, a recording medium having recorded thereon the moving picture data encoded using the prediction encoding system and a method and apparatus for decoding moving picture data encoded using the predictive encoding method. This invention also relates to a method and apparatus for judging continuous reproducibility of data encoded using the prediction encoding system.
2. Description of the Related Art
The conventional recording/reproducing apparatus for an optical disc generally includes an encoding unit and a decoding unit for companding a picture in accordance with an MPEG (Mcving Picture Experts Group) system. Picture signals are recorded/reproduced as the picture is compressed or expanded using this MPEG system.
In this MPEG system, a picture constituting a moving picture (picture of a field or a frame) is encoded in accordance with a picture type of one of I-, P- and B-pictures, by way of compressing the picture.
The I-picture is in which encoding is completed within one picture, is encoded independently of other pictures. Thus, the I-picture is used as an entry point for random accessing or error restoration.
The P-picture is obtained on predictive coding from a temporally past I- or P-picture. Thus, for decoding this P-picture, the temporally past I- or P-pictures need to be already decoded.
The B-picture is obtained on predictive coding in the forward direction, backward direction or in both directions from a temporally future I- or P-picture. Thus, for decoding this B-picture, temporally past and future I- or P-pictures need to be already decoded.
Thus, in the MPEG system, pictures are compressed efficiently by inter-picture predictive coding, while random accessing can be had to the compressed moving pictures.
Also, in the MPEG system, these different sorts of pictures are compressed into a data stream made up of an optional number of pictures grouped together (group-of-pictures or GOP). The MPEG system provides that at least one I-picture be present in each GOP. This renders possible random accessing to moving pictures compressed on the GOP basis.
It is now assumed that, in the above-described conventional recording/reproducing apparatus, signals compressed in accordance with the MPEG system are to be reproduced.
On a recording medium, encoded data of a datastream shown for example in FIG. 1 is recorded. In the conventional recording/reproducing apparatus, the datastream recorded as shown in FIG. 1A is decoded to display the decoded datastream in the picture sequence shown in FIG. 1B. In FIG. 1, symbols affixed to the pictures xe2x80x9cIxe2x80x9d, xe2x80x9cPxe2x80x9d and xe2x80x9cBxe2x80x9d denote I-, P- and B-pictures, respectively, each suffix number indicating the display order in the GOP, that is the so-called temporal reference.
For reproducing the encoded data of the datastream shown in FIG. 1A by the conventional recording/reproducing apparatus, a picture I0 is decoded first. Since the I-picture is complete in itself, the conventional recording/reproducing apparatus can decode I0 by itself without decoding other pictures. The conventional recording/reproducing apparatus then proceeds to decode forwardly predictive-coded P2, based on the decoded I0. Since the P-picture is predictive-coded from the temporally previous I- or P-picture, it is necessary for the conventional recording/reproducing apparatus to decode I0 prior to decoding this P2. The conventional recording/reproducing apparatus then proceeds to decode the bidirectionally coded B1 based on the decoded !0 and P2. Since the B-picture is bidirectionally coded from the temporally forward and backward I- or P-pictures, it is necessary for the conventional recording/reproducing apparatus to decode I0 and P2 prior to decoding this B1. Thus, the conventional recording/reproducing apparatus decodes the encoded data of the datastream shown in FIG. 1A in the sequence of I0xe2x86x92P2xe2x86x92B1xe2x86x92P4xe2x86x92B3xe2x86x92P6xe2x86x92B5xe2x86x92I8xe2x86x92B7xe2x86x92P10xe2x86x92B9xe2x86x92 . . . .
If, in the conventional recording/reproducing apparatus, the pictures decoded in the above sequence are to be displayed, the picture sequence is interchanged as shown in FIG. 1B to male a display in the sequence of I0xe2x86x92B1xe2x86x92P2xe2x86x92B3xe2x86x92P4xe2x86x92B5xe2x86x92P6xe2x86x92B7xe2x86x92I8xe2x86x92B9xe2x86x92P10xe2x86x92 . . . .
Meanwhile, in the conventional recording/reproducing apparatus, if the recording medium is random-accessible, it is possible to have random access to the encoded data recorded by the MPEG system. Thus, it is possible with the conventional recording/reproducing apparatus to skip certain pictures by first reproducing pictures up to the P-picture shown at SA and skipping the ensuing pictures to reinitiate reproduction at the B-picture shown at a point SB (picture B3). This skipping of certain pictures is hereinafter termed skipping and picture reproduction from a certain picture to a different distant picture by skipping intermediate pictures is termed skip reproduction. Also, a picture directly previous to the start of the skipping, for example, a picture SA shown in FIG. 2, is termed an out-point picture, while a picture at which reproduction is initiated after the end of the skipping, for example, a picture SB shown in FIG. 2, is termed an in-point picture.
However, if this skip reproduction is performed on the conventional recording/reproducing apparatus, there are occasions wherein temporal continuity of reproduced pictures is interrupted and lost.
If, for example, the in-point picture is a B-picture, it is necessary to previously decode an I- or a P-picture required for decoding this B-picture, in which case temporal continuity of reproduced pictures is interrupted and lost. More specifically, with reference to an instance shown in FIG. 2, since the in-point picture is B3 with the conventional recording/reproducing apparatus, at least I0, P2 and P4 need to be decoded in order to decode this B3. Thus, with the conventional recording/reproducing apparatus, no picture can be displayed while I0, P2 and P4 are decoded, such that the picture continuity is interrupted and lost.
As described above, it is not possible with the conventional recording/reproducing apparatus to achieve seamless reproduction of pictures ahead and at back of skipping on the occasion of skipping reproduction.
Although the above example is pertinent to picture compression in accordance with the MPEG system, temporal continuity in skipping reproduction is similarly interrupted and lost even in case of inter-picture predictive coding in which the difference between pictures is found in order to exploit the inter-picture correlation and the difference thus found is encoded.
It is therefore an object of the present invention to provide a decoding method and apparatus for decoding moving picture data in which continuity of moving pictures before and after the skipping is maintained to enable skipping reproduction.
It is another object of the present invention to provide a recording method and apparatus for recording moving pictures in such a manner that a reproduction starting picture and a reproduction termination picture can be decoded and outputted correctly at the thine of reproducing moving picture data, and that, at the time of skipping reproduction, skipping from the reproduction termination picture to the reproduction starting picture can be effected seamlessly.
It is a further object of the present invention to provide a recording medium on which moving picture data are recorded thereon so that the reproduction starting picture and the reproduction termination picture can be correctly decoded and outputted at the time of reproducing moving picture data, and so that, at the time of skipping reproduction, skipping from the reproduction termination picture to the reproduction starting picture can be effected seamlessly.
It is a further object of the present invention to provide a method and apparatus for decoding moving picture data so that the reproduction starting picture and the reproduction termination picture can be decoded and outputted correctly and so that, at the time of skipping reproduction, skipping from the reproduction termination picture to the reproduction starting picture can be effected seamlessly.
It is yet another object of the present invention to provide a method and apparatus for judging feasibility of continuous reproduction of moving picture data at the time of skipping reproduction.
In one aspect, lie present invention provides a decoding apparatus for data of moving pictures for decoding encoded data of moving pictures encoded using a predictive encoding system, including decoding means for decoding first encoded data made up of moving pictures up to a preset moving picture and second encoded data made up of moving pictures beginning from a moving picture displayed next to the preset moving picture at a speed faster than the display speed of the encoded data, and output control means for controlling the outputting of decoded moving pictures based on the time management information of each moving picture of the encoded data.
With the decoding apparatus for multiplexed data according to the present invention, the decoding means time-divisionally decoding the first encoded data and the second encoded data.
Also, with the decoding apparatus for multiplexed data according to the present invention, there is provided storage means for temporarily storing decoded moving picture data.
With the present moving picture data decoding apparatus, the first encoded data and the second encoded data are decoded at a decoding speed faster than the display speed.
In another aspect, the present invention provides a decoding method for data of moving pictures for decoding encoded data of moving pictures encoded using a predictive encoding system including a decoding step for decoding first encoded data made up of moving pictures up to a preset moving picture and second encoded data made up of moving pictures beginning from a moving picture displayed next to the preset moving picture at a speed faster than the display speed of the encoded data, and an output control step for controlling the outputting of decoded moving pictures based on the time management information of each moving picture of the encoded data.
In the present moving picture data decoding method, the decoding step time-divisionally decodes the first and second encoded data during the decoding step.
In the present moving picture data decoding method, there is provided a storage step for temporarily storing decoded moving picture data.
In the present moving picture data decoding method, the first and second encoded data are decoded at a decoding speed higher than the display speed.
In a further aspect, the present invention provides a decoding apparatus for data of moving picture for decoding encoded data of moving pictures encoded using a predictive encoding system, including first decoding means for decoding encoded data up to a moving picture whose display is completed at a first time point corresponding to a preset display time point, second decoding means for decoding encoded data beginning from a moving picture which starts to be displayed at a second time point skipped a preset time interval from the first time point, output control means for controlling the outputting of a moving picture decoded by the first decoding means or the second decoding means when the time management information of the encoded data coincides with reference synchronization signals, and switching means for changing the reference synchronization signals to the second time point when the reference synchronization signals are equal to the first time point for switching the moving picture output-controlled by the output control means to the picture decoded by the second decoding means.
In the present moving picture data decoding apparatus, a picture decoded by the first decoding means and whose display is terminated at a first time point and a picture decoded by the second decoding means and whose display is started at a second time point are switched and outputted simultaneously with switching of the reference synchronization signal.
In a further aspect, the present invention provides a decoding method for data of moving picture for decoding encoded data of moving pictures encoded using a predictive encoding system, including a first decoding step for decoding encoded data up to a moving picture whose display is completed at a first time point corresponding to a preset display time point, a second decoding step for decoding encoded data beginning from a moving picture which starts to be displayed at a second time point skipped a preset time interval from the first time point, an output control step for generating a reference synchronization signal and for controlling the outputting of a moving picture decoded by the first decoding step or the second decoding step when the time management information coincides with reference synchronization signals and a switching step for changing the reference synchronization signal to the second time point when the reference synchronization signal is equal to the first time point for switching the moving picture output-controlled by the output control step to the picture decoded by the second decoding step.
In the present moving picture data decoding method, a picture decoded by the first decoding means and whose display is terminated at a first time point and a picture decoded by the second decoding means and whose display is started at a second time point are switched and outputted simultaneously with switching of the reference synchronization signal.
In a further aspect, the present invention provides a recording apparatus for moving picture data including encoding means for encoding moving picture data using a predictive encoding system, designation information supplying means for supplying the information designating a decoding starting picture and a display starting picture in the moving picture delta and for supplying the information designating a decoding terminating picture and a display terminating picture in the moving picture data and recording means for recording moving picture data encoded by the encoding means and the designation information supplied by the designation information supplying means.
In the present moving picture data recording apparatus, the information specifying a decoding starting picture and a display starting picture in moving picture data and the information specifying the decoding terminating picture and the display terminating picture in the moving picture data are recorded on the recording medium.
In a further aspect, the present invention provides a recording method for moving picture data including encoding means for encoding moving picture data using a predictive encoding system, supplying the information designating a decoding starting picture and a display starting picture in the moving picture data and for supplying the information designating a decoding terminating picture and a display terminating picture in the moving picture data, and recording encoded moving picture data and the supplied designation information.
In the present moving picture data recording method, the information specifying a decoding starting picture and a display starting picture in moving picture data and the information specifying the decoding terminating picture and the display terminating picture in the moving picture data are recorded on the recording medium.
In a further aspect, the present invention provides a recording medium on which there are recorded the information designating a decoding starting picture and a display starting picture in moving picture data and the information designating a decoding terminating picture and a display terminating picture in moving picture data along with encoded data of moving pictures encoded using the predictive encoding system.
On the present recording medium, there are recorded the information specifying a decoding starting picture and a display starting picture in moving picture data and the information specifying the decoding terminating picture and the display terminating picture in the moving picture data.
In a further aspect, the present invention provides a decoding apparatus for moving picture data including decoding means for decoding encoded data of moving pictures encoded using a predictive encoding system, and control means for controlling the decoding and the outputting of moving picture data by the decoding means based on the information designating a decoding start picture and a display start picture in moving picture data and on the information designating a decoding terminating picture and a display terminating picture in the moving picture data.
In the present moving picture data decoding apparatus, encoded data of a moving picture encoded using the inter-picture predictive encoding system are decoded based on the information specifying the decoding starting picture and the display starting picture in moving picture data and on the information specifying the decoding terminating picture and the display terminating picture in the moving picture data and the decoded data are outputted.
In a further aspect, the present invention provides a decoding method for moving picture data including decoding encoded data of a moving picture encoded using a predictive encoding system based on the information specifying a decoding starting picture and a display starting picture in moving picture data and on the information specifying a decoding terminating picture and a display terminating picture in moving picture data, and outputting the decoded data.
In the present moving picture data decoding method, encoded data of a moving picture encoded using the inter-picture predictive encoding system are decoded based on the information specifying the decoding starting picture and the display starting picture in moving picture data and on the information specifying the decoding terminating picture and the display terminating picture in the moving picture data and the decoded data are outputted.
In yet another aspect, the present invention provides a continuous reproduction possibility verifying method and apparatus for encoded data wherein, in reproducing a series of encoded data encoded using a predictive encoding system by decoding pictures of the encoded data from a first display starting point picture of the encoded data to a first display terminating point picture of the encoded data, designated as an out-point picture in skipping processing of the encoded data, then skipping the decoding from the first display terminating point picture to a second display starting point picture designated as an in-point picture in the skipping processing, and by decoding pictures from the second display starting point picture to a second display terminating point picture, it is verified, based on the time difference between a display time point of the first display starting point picture and a display time point of the first display terminating point picture, whether or not continuous display of the first display terminating point picture and the second display starting point picture is possible.